// This code is derived from jcifs smb client library <jcifs at samba dot org>
// Ported by J. Arturo <webmaster at komodosoft dot net>
//  
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
using System;
using SharpCifs.Util.Sharpen;

namespace SharpCifs.Util
{
    /// <summary>This is an implementation of the HMACT64 keyed hashing algorithm.</summary>
    /// <remarks>
    /// This is an implementation of the HMACT64 keyed hashing algorithm.
    /// HMACT64 is defined by Luke Leighton as a modified HMAC-MD5 (RFC 2104)
    /// in which the key is truncated at 64 bytes (rather than being hashed
    /// via MD5).
    /// </remarks>
    public class Hmact64 : MessageDigest
    {
        private const int BlockLength = 64;

        private const byte Ipad = unchecked(unchecked(0x36));

        private const byte Opad = unchecked(unchecked(0x5c));

        private MessageDigest _md5;

        private byte[] _ipad = new byte[BlockLength];

        private byte[] _opad = new byte[BlockLength];

        /// <summary>Creates an HMACT64 instance which uses the given secret key material.</summary>
        /// <remarks>Creates an HMACT64 instance which uses the given secret key material.</remarks>
        /// <param name="key">The key material to use in hashing.</param>
        public Hmact64(byte[] key)
        {
            int length = Math.Min(key.Length, BlockLength);
            for (int i = 0; i < length; i++)
            {
                _ipad[i] = unchecked((byte)(key[i] ^ Ipad));
                _opad[i] = unchecked((byte)(key[i] ^ Opad));
            }
            for (int i1 = length; i1 < BlockLength; i1++)
            {
                _ipad[i1] = Ipad;
                _opad[i1] = Opad;
            }
            try
            {
                _md5 = GetInstance("MD5");
            }
            catch (Exception ex)
            {
                throw new InvalidOperationException(ex.Message);
            }
            EngineReset();
        }


        protected byte[] EngineDigest()
        {
            byte[] digest = _md5.Digest();
            _md5.Update(_opad);
            return _md5.Digest(digest);
        }

        protected int EngineDigest(byte[] buf, int offset, int len)
        {
            byte[] digest = _md5.Digest();
            _md5.Update(_opad);
            _md5.Update(digest);
            try
            {
                _md5.Digest(buf, offset, len);

                return len;
            }
            catch (Exception)
            {
                throw new InvalidOperationException();
            }
        }

        protected int EngineGetDigestLength()
        {
            return _md5.GetDigestLength();
        }

        protected void EngineReset()
        {
            _md5.Reset();
            _md5.Update(_ipad);
        }

        protected void EngineUpdate(byte b)
        {
            _md5.Update(b);
        }

        protected void EngineUpdate(byte[] input, int offset, int len)
        {
            _md5.Update(input, offset, len);
        }

        public override byte[] Digest()
        {
            return EngineDigest();
        }

        public override int GetDigestLength()
        {
            return EngineGetDigestLength();
        }

        public override void Reset()
        {
            EngineReset();
        }

        public override void Update(byte[] b)
        {
            EngineUpdate(b, 0, b.Length);
        }

        public override void Update(byte b)
        {
            EngineUpdate(b);
        }

        public override void Update(byte[] b, int offset, int len)
        {
            EngineUpdate(b, offset, len);
        }
    }
}
